Responsive red carbon dots with dual-wavelength emission for anti-counterfeiting

Fluorescence (FL)-based anti-counterfeiting technologies relying on visible color variations are increasingly vulnerable to counterfeiting, posing a critical challenge to security levels. To address this issue, as proof-of-concept research, we constructed a concealed spectral anti-counterfeiting system using dual-emission red carbon dots (R-CDs), aiming to verify the feasibility of achieving high anti-counterfeiting security through visually invisible but spectroscopically distinguishable FL spectral changes. The as-prepared R-CDs feature two distinct red FL emission peaks at 601 nm and 650 nm, respectively. A notable selective FL response was observed upon interaction with Al³⁺: the main emission at 601 nm was drastically quenched, while the shoulder emission at 650 nm remained detectable, resulting in obvious spectral differentiation. Owing to the limited resolution of the human eye in the red light region, this spectral variation is visually indistinguishable under green light excitation but can be accurately identified using a FL spectrometer. This study proposes a proof-of-concept design for concealed spectral anti-counterfeiting, offering a new approach to enhance anti-counterfeiting security and providing promising potential for advanced information encryption scenarios.